In the present and future technology generations, fast and accurate circuit simulations and analysis are required to capture rapidly-changed device features, intrinsic device fluctuation and random mismatch among adjacent devices. Numerical device simulations (e.g., technology computer-aided design (TCAD), such as Synopsys TCAD available from Synopsys, Inc., Mountain View, Calif.) are based on physical drift-diffusion or hydrodynamic transports which are partial differential equations and are accurate. However, simulation run-time is significantly slow for circuit-level simulations. Table-look-up based circuit analysis is very fast, but table-look-up methods are not accurate due to many interpolated regions. See, for example, A. Rofougaran et al., “A Table Lookup FET Model for Accurate Analog Circuit Simulation,” IEEE Trans. CAD, vol. 12, no. 2, pp. 324-335 (February 1993). Simulation program with integrated circuit emphasis (SPICE), a traditional circuit simulator, is also widely used. However, due to non-linear and discontinuous field-effect transistor (FET) characteristics, only limited accuracy can be offered to circuit design. Also, reliable SPICE models are not available in the early stages of the design process (and/or before hardware data is available), and the development of models takes a long time and involves many complex steps.
Thus, TCAD simulations involve extensive amounts of computational time which cannot be directly used in circuit simulations. Complementary metal-oxide semiconductor (CMOS) technologies (including static random access memory (SRAM)) are getting more complex and thus it is becoming more difficult to predict performance/power and yield of these circuits. SPICE (i.e., an algebraic equation-based model) is fast and predictable, but still exhibits discrepancies between model and hardware (or extensive numerical simulations). A look-up table based tool is faster but not accurate due to many interpolations.
Therefore, circuit simulation techniques that are both fast and accurate would be desirable.